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Calculate the resistance

  • #1
323
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Homework Statement


In the picture below, is a circuit of constant direct current. The receiver is made of a changable resistor with resistance R. If the reciever delivers maximum electrical power its resistance is
a)9 b)6 c)3 d)1.5 e)0.5

Homework Equations


Im having trouble finding the equation for this

The Attempt at a Solution


I cant find the theory of this curcuit, the equations that fit so can you guide me a little in any way that could help?
 

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Answers and Replies

  • #2
cnh1995
Homework Helper
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Look up 'maximum power transfer theorem'. Are you familiar with the Thevenin's theorem?
 
  • #3
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Look up 'maximum power transfer theorem'. Are you familiar with the Thevenin's theorem?
I am not but i will check it out now then try to apply something to the problem and get back to you :)
 
  • #5
cnh1995
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  • #6
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For maximum power transfer, the load resistance should be equal to the Thevenin resistance of the circuit viewed from the load terminals. Here, your load resistance is the variable resistor. Can you proceed with this?
Is the equation for thevenin resistance the one in the picture uploaded? If so how to get it if not all three resistors are known?
 

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  • #7
cnh1995
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If so how to get it if not all three resistors are known?
For computing Thevenin resistance seen from the load terminals, you should remove the load resistance (variable resistance) and compute the resistance of the circuit seen from the load terminals.
 

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